Raised a second question, however, the file ASSET also seems to manage the Owner & Service Tag No. I thought it would be useful to put the actual number back in there rather than leave the XXXXXXXX's displayed, and to set myself up as the owner.

Use the parameter asset /o 'NewOwnerName' and it also worked a treat, but...

Used the parameters asset /s 'NewSerNo' but it asked for a SETUP password. None of the BIOS passwords are enabled and I was not aware that there was a separate setup password.